~ Earthquake ~

[MysteRy]

Earthquake



Earthquakes, also known as temblors, occur when the tectonic plates of the earth move while floating on the molten rock that is earth’s core. These tectonic plates, at times, collide against each other and affect the earth’s surface; these effects can either be drastic or barely felt. The tectonic plates create immense stress which, when released, sends seismic waves or vibrations across the earth’s surface. Lasting from few seconds to minutes, these earthquakes are followed by aftershocks which are sometimes more intense than the main quake. Among the countless quakes that hit the earth’s surface, only 20% are destructive while others cause only mild tremors. However, these tremors are quite unpredictable and occur anywhere, at any time. Though most of the earthquakes occur due to the plates’ collision, even volcanic eruptions and meteorological crashes can trigger such tremors. 75% of the world’s earthquakes occur in a region called ‘Pacific ring of Fire’. This region has plenty of fault zones in its tectonic plates which lead to frequent clashes.

Amazing & Interesting Facts About Earthquake

There are about 20 moving plates which form the earth’s surface. When these plates collide with each other, breakage and stress in earth’s crust can be seen and felt. With this stress, energy is released as seismic waves that we experience as earthquakes.

As per U.S Geological survey, more than three million earthquakes occur every year, averaging to about 8000 quakes in a day and 11 in every second. The number of people who die due to earthquakes every year is more than 10,000. However, only 100 earthquakes actually cause any serious damage.

A normal earthquake lasts 60 seconds.                     

The earthquake which occurred in Indian Ocean on December 26, 2004 was of the magnitude 9.0 and killed almost 160,000 people.

The ‘focus’ of an earthquake is the point where it actually starts while epicentre is a point on the surface of the earth, directly above the focus.

Earthquakes generate two types of waves, viz., body waves and surface waves. The time of the arrival of the various body waves enable the seismologists to locate the epicentre.

An earthquake which occurs after the main quake is the aftershock. In few cases, these aftershocks are more intense than the main quake.

Experts use Richter scale and Magnitude scale to analyse the amount of energy released during a quake.

The study of earthquakes is known as seismology. Seismograph, used to measure, detect and record the vibrations of earthquakes, was invented in 1751.

One of the most lethal earthquakes occurred in Shansi China in 1556 when 830,000 people died due to the tremors. The deaths occurred mainly due to the collapse of the caves that people lived in. The most deadly earthquake of recent times occurred in Sumatra in 2004 where almost 255,000 people died.

The largest recorded earthquake occurred in Chile in 1960 with a magnitude of 9.2 on Richter scale.

Earthquakes occur on moon as well and are called moonquakes. However, these are of lesser magnitude and smaller in comparison to those that occur on earth.

Alaska, in United States, is the most earthquake prone region in the world. An earthquake, with a magnitude of 8, occurs once in every fourteen years here.

The occurrence of earthquake is not dependent on weather which means earthquakes can occur in any type of weather.

Countries like Japan use great defence mechanisms while constructing houses to make them earthquake resistant. Good engineering prevents the collapse of buildings during earthquakes.

Animals can sense earthquakes much before they occur.

A normal earthquake has a depth of 50 miles below earth’s surface.

Around 10,000 earthquakes occur every year in Southern California in United States.

It was Aristotle, the Greek Philosopher, who found out that soft ground shakes more during earthquakes than hard grounds.

During large earthquakes, people experience a swaying or a jerking motion followed by a pause and then a strong jerking.

In urban areas, the earthquakes cause more destruction as the seismic waves can weaken the manmade structures and force them to collapse.

The peaks in the Himalaya-Karakoram mountain ranges were formed due to the moving of the tectonic plates millions of years ago. Similar movements can now be felt in the Andaman & Nicobar regions of India.

Though the exact prediction of earthquake is far from being achieved, gathering information and data from the previous quakes enable the scientists to predict the future quakes to a certain extent.

[MysteRy]

Types Of Earthquakes



Earthquakes, caused by the propagation of seismic waves, are tremendous natural forces which, since time immemorial, have caused a lot of devastations. These seismic waves are produced by the sudden release of energy amassed in the earth’s crust. Earthquakes occur along the regions of geological faults and narrow zones, due to the corresponding movement of the rock masses. The most sensitive or earthquake prone regions of the world lie at the fringes of the gigantic tectonic plates that constitute the Earth’s crust. However, very little was known about the causes and types of earthquakes, until the 20th century. But, with the evolution of the ‘seismology’, scientists have been able to understand the nature of this great devastating force more and more. Earthquakes often occur in regions away from fault lines. However, earthquakes don’t always occur naturally and there are several manmade causes also for their occurrence.

Different Types Of Earthquakes 

Tectonic Earthquakes
The earth’s crust comprises of gigantic fragments or plates, called tectonic plates. These plates can slide over the plastic aesthenosphere, uppermost layer of the mantle.

The tectonic plates have a considerable degree of freedom and can slide in any direction, away from each other, towards each other and even past each other; it is this third movement which causes the tremors on earth’s surface.

American geologist Harry Fielding Reid explained the tectonic earthquakes for the first time in his ‘elastic rebound theory’, after the San Andreas Fault ruptured in 1906 and caused the infamous San Francisco earthquake.

The movement of the tectonic plates is the most common cause of earthquakes all over the world.

There are a number of crustal plates, which have been split into several smaller plates. These plates are around 80 kilometers in thickness, and are constantly moving. The speed of their movement has been found to be somewhere around 10 to 130 mm per year.

However, the nature of their movement is not symmetrical and many geological formations such as mountains and rift valleys, and phenomena such as volcanoes, earthquakes, faulting, etc. are due to different types of interactions at plate boundaries.

The intensity of these earthquakes can be extremely high and has been responsible for severe devastations throughout the history of earth.


Volcanic Earthquakes
Volcanic earthquake are caused by volcanic eruptions and are not a very common occurrence; these are at least much less frequent than the tectonic earthquakes.

Volcanic earthquakes can be further divided into two categories, viz., volcanic tectonic earthquakes and long period volcanic earthquakes.

The earthquake which follows a volcanic eruption is known as the volcanic tectonic earthquake.

Typically every volcanic eruption leads to a great release of magma which creates a great vacant space which is then filled in by a great mass of rocks. The movement of these rocks towards the empty space creates shock waves which propagate across the earth’s surface.

It also happens that the lava which gets discharged during any volcanic eruption falls on the very outlet from which it is ejected. It seals the vent and an enormous pressure is created. However, the closure created by the Lava can’t sustain the pressure for long and soon a great explosion follows. This explosion causes a long period volcanic earthquake which often ranks high on the Richter scale.

A long period of volcanic earthquake follows a great volcanic eruption. After a volcanic eruption, the magma undergoes a change of heat, which begets seismic waves resulting in an earthquake.


Collapse Earthquakes
Much inferior in magnitude as compared to the two aforementioned earthquakes, a collapse earthquake occurs in the regions around underground mines.

Also known as the mine burst, this type of earthquake is stirred due to the release of pressure stored in the rocks. Due to this outburst of pressure, the roof of the mine or cavern collapses, releasing seismic waves which cause the tremors.

This type of small scale earthquake can be frequently felt in areas where there are underground mines.


Explosion Earthquakes
An explosion earthquake is caused by nuclear and chemical devices. Underground nuclear explosions release an enormous amount of energy which creates powerful seismic waves in the area around where the tremors can be felt.

In the 1930s, during the nuclear tests in America, and in 1998, during the nuclear tests in Pokharan, India, many small villages and towns in the surrounding regions felt powerful quakes.

Most natural earthquakes are caused by the movement of the tectonic plates. However volcanic eruptions have also been responsible for some of the major earthquakes throughout the history of the earth. And nowadays, even manmade nuclear inventions can trigger this phenomenon.

[MysteRy]

How Is An Earthquake Measured



There are two numbers generally measured, whenever an earthquake occurs - its magnitude and intensity. While magnitude is termed as the strength of the earthquake, the intensity of the natural calamity varies from place to place, depending upon a number of factors. Two scientists are associated with the invention of the scales for the measurement of each of the two numbers - Charles F Richter and Giuseppe Mercalli. In the following lines, we have examined the two terms — magnitude and intensity — in detail, and provided information on how they are measured.

Measuring Magnitude & Intensity Of Earthquakes


Magnitude
In 1935, an American seismologist, Charles F Richter, made use of a logarithmic scale to measure the magnitude (the size and strength) of an earthquake. Known as Richter scale, it was based on the amplitude of the waves, measured by a seismograph. When the magnitude is measured, it is adjusted to account for the distance between the seismograph and the epicenter of the quake. The numbers shown by Mercalli scale vary according to the destruction caused by an earthquake at each level.
 
The magnitude of an earthquake is recorded in the ascending order of destruction, starting from I to XII. When the scale measures I as the magnitude, the earthquake is considered to have the slightest effect on buildings and human beings. On the other extreme, the calamity with a magnitude of XII is regarded as severely destructive. Significant damage to buildings can occur when the magnitude of earthquake is VII and above.


Intensity
Italian scientist Giuseppe Mercalli invented Mercalli scale in 1902. It is used to measure the intensity of an earthquake, based upon the observation of destruction caused by the calamity at a particular location. The intensity may vary from place to place. The distance from the epicenter, design and quality of construction of local building and the type of surface beneath the buildings are the factors responsible for the variation of intensity of an earthquake from one place to the other. 
The seismographs near the epicenter of the earthquake measure its intensity, ranging from 1 to 9. The lowest intensity, number 1, is not felt at the surface. Little damage is caused, when the intensity is recorded as 4. The number 6 corresponds to a strong earthquake, clearly felt over a wide area. The intensity of earthquake, noted as 7 and 8 on the Richter scale, is considered as highly destructive, damaging the buildings and life up to 100 km from epicenter. The intensity of 9 has not been recorded till date. Such a high intensity is regarded as an earthquake that can devastate life up to 1000 km from the epicenter.

[MysteRy]

Earthquake Safety Tips



It is a lovely Saturday morning; the sun is shining bright, the sky is blue and cloudless, the birds are twittering and you are sipping your hot cup of coffee. Suddenly, you sense a jolt and feel your comfortable sofa swinging from side to side like a cradle. Before you can even realize what is happening, you feel the tremors getting stronger and find yourself being gripped by fear. A strong earthquake is jolting the senses right out of you! In a panicky situation, usually your mind races as to what to do, though you don’t really seem to come to a conclusion. Given here are a few earthquake safety tips, which, when kept in mind can help you be safe during an earthquake.

What to do in Case of Earthquake

Earthquakes can be very scary and can make any relaxed person tensed immensely. But you need to keep your mind stable in order to make sure you are safe. Be calm and try not to run here and there.

Take time to move out in the open away from buildings and electric wires, if you are outside. If you manage to come out of your house, go to an open space like a garden or a park where you will be a lot safer.

If you live quite some floors above in your building, try to seek shelter near a bulky object such as a sofa. Curl up and sit on the floor and make sure you are not near a window, mirror, fireplace, gas stove or have heavy paintings or wall hangings above you. Avoid using the lift or escalators.

Some people say you should stand on a doorway. That is just not the case. Heavens forbid, if the doorway jambs are weak, they might fall on you, crushing and killing you almost instantly. Also, if people want to pass through that door, you may trap them and yourself by standing there. Leave all doorways free.

Another important thing to keep in mind is that you must not climb down the stairs during an earthquake. Stairs can swing wildly, due to fact they don’t have beams or pillars supporting them. They have the maximum chances of collapsing even if the building remains intact. In case the tremors stop, after a few seconds, just climb down the stairs at a rapid pace and move out of the building, but don’t run.

Earthquakes usually crack gas pipes and snap electrical wires. If you smell gas at your place, open all windows and let it out. Turn off the main gas valve to stop any more gas leakage. Don’t light candles or lighters and create an even bigger disaster.

If you are driving and feel a jolt, stop your car at the side of the road and get out. Make sure you are not on a bridge, under a flyover or near electric cables. Bridges and overhead roads have the maximum dangers of falling.

[MysteRy]

How To Handle Earthquake



Natural calamities always occur without notifying anybody. However, if you get warning signals about the potential disaster, you should make sure to be vigilant on your part. One such calamity, that comes unbridled, is earthquake. During an earthquake, you should not panic about what to do and how to escape. Instead, you should formulate ways to rescue yourself and others from the disaster and avoid serious injuries. You should take safety measures, depending upon the intensity of the earthquake.

What To Do In An Earthquake

During An Earthquake
During an earthquake, if you are indoors, do not panic. Find a cover - a sturdy piece of furniture, like a desk or table, to cover yourself. Get under the furniture and lie down.

Protect your head and neck with hands and arms. Stay away from glass, heavy furniture, fireplaces and electronic equipments.

Keep distance from windows and outside walls as well. Cling on to a hard piece of furniture.

Hold on to the furniture firmly and be prepared to move with it. Do not release the grip until the tremor is over.

If you are outdoors, get into an open space, away from buildings. Do not stand under electric posts or anything else that could collapse on you.

In case you are driving, pull your car out of the traffic, and stop it at the side of the road. Park the vehicle in an open area, away from light posts and power lines. Keep sitting inside it until the shaking is over.

During an earthquake, when you are in a crowded place such as stadium or theatre, avoid panicking. Do not create chaos, by rushing for the exit. To get out of the area, use stairs instead of escalators. Move out in an orderly manner.


After An Earthquake
Check for injuries to the people around you.

Try to move the injured persons out of the debris. Clean up spilled medicines and drugs and other potentially harmful chemicals.

Find out whether the earthquake has resulted in fire hazards.

Do not touch power lines, as they may give you an electric shock.

Wear sturdy shoes, when you are moving in the areas near debris or broken glass.

Inspect the area and check for any gas leaks. In case you detect the smell of leaking gas, do not light candles or matches. Provide ventilation for the area by opening all the windows. Let the gas move out of the room.

Do not re-enter any devastated building, until all the repairs are done and the place has been declared safe.